Goody was one of 33,598 starters to have contributed towards an estimated £35m being raised for charity this year. She raced wearing a Gucci bum bag and admitted afterwards she had prepared for the event on a diet of Chinese meals.
Stephen George, director of community appeals at the NSPCC, said the charity was concerned that she had not trained as much as its other runners.
"We're very grateful for her support," he said. "But we advised her last week after her health scare that we thought she shouldn't be running."
Goody's efforts were appreciated by one well-wisher on the JustGiving site, who wrote: "Well done, dear girl! Eighteen miles? Awesome! Feel proud of your efforts."
Five-times Olympic rowing champion Sir Steve Redgrave broke the individual fundraising record with £1.3m of pledges.
Official marathon charity the Anthony Nolan Trust claimed one of its runners, who sported a 3.3m-high costume, had broken the world record for tallest costume worn in a marathon.
Co-official charity the Stroke Association was expecting £1m from its 500 runners this year.